1. Cross Reference to Related Applications
The invention pertains to a novel interface between at least one Control Unit and at least one Transceiver Unit of a two-way radio that is interrelated to the subject matter of the related copending patent applications entitled (1) Control System for Microprocessor And Software Enhanced Communications Equipment U.S. application Ser. No. 031,004 filed Mar. 27, 1987; (2) Computerized Multistandard, Field Convertible, Multiregional/Multiservice, Remote Controllable, Remote Programmable Mobile Two-Way Radio System With Digital Serial Bus Link, Built-In Programmer and Autodiagnostics, U.S. application Ser. No. 030,743 filed Mar. 27, 1987; (3) Audio Blanking Fill-In Method And Apparatus For Priority Multi-Channel Receivers, U.S. application Ser. No. 030,594 filed Mar. 27, 1987 which title was amended to read, An Interrupted Audio Fill-In System For Noise Reduction and Intelligibility Enhancement In Multi-Channel Scanning Receiver Applications, and issued as U.S. Pat. No. 4,868,891 on Sept. 19, 1989; (4) Variable Time Inversion Algorithm Controlled System For Multi-Level Speech Security, U.S. application Ser. No. 030,499, filed Mar. 27, 1987 and refiled on May 1, 1989 as U.S. application Ser. No. 07/346,282, the disclosures of which are incorporated herein by reference and (5) Combined Phase And Frequency Modulator For Modulating An Information Signal, filed Mar. 27, 1987, application Ser. No. 030,592, and issued as U.S. Pat. No. 4,739,288, on Apr. 19, 1988.
2. Field of the Invention
This invention pertains generally to two-way radio communications equipment, which includes two-way land/mobile communications equipment such as those used, for example, in law enforcement vehicles and headquarters. More particularly the invention pertains to a Bidirectional Digital Serial Interface System For Communicating Digital Signals Including Digitized Audio Between Microprocessor-Based Control And Transceiver Units of Two-Way Radio Communications Equipment.
The inventions provides a novel new Digital Serial Interface System for communicating digital signals, including digitized audio, between microprocessor-based Control and Transceiver Units of two-way land/mobile or other communications equipment.
With the advent of increasingly powerful yet cost-effective microprocessors and memory devices, it has become more desirable to use digital techniques and microprocessor/memory devices in modern two-way radio communications equipment. Such new technology increases the capabilities and versatility of the communications equipment. In many cases, however, it necessitates new approaches in the design of various systems, the sub-systems, the peripherals and interfaces of the new equipment utilizing such enhancements.
3. Description of the Prior Art
Law enforcement vehicular officers and other large or stringent users have vastly more advanced needs than before, including the need to access different channels, variable power requirements, various speech/audio scrambling requirements, ability to enter the nationwide telephone network, ability to access permanent site repeaters, ability to make a vehicular radio inoperative as, for example, if the vehicle is stolen by criminals with whom apprehension is desired, the ability to receive and perhaps transmit pictorial data such as fax (facsimile) for pictures of criminals, cars, etc., ability to transmit and receive alphanumeric data such as vehicle license numbers, addresses, names and the like.
Therefore numerous physical electrical wires are needed to connect between the control unit, usually under the dashboard, and the transceiver unit, usually in the trunk. These wires in a bundle or unitary cable form become a physical burden when laying them between trunk and dash. Further they may radiate energy themselves when in use. Still further, they do not easily permit the noncustomized use of multiple transceivers as no networking form between a control unit and multiple transceivers is practical unless a network protocol is built into the system. Again one notes that such capabilities require a unitary digital system, previous to this invention not achieved. See U.S. Pat. No. 4,232,390 McEvilly, Jr. as to one control unit controlling a multiple number of transceivers.
This invention specifically addresses the interface aspects of new generation communications and control equipment employing extensive use of microprocessors in both Control and Transceiver Units, memory devices and other digital techniques. With such designs, each end of microprocessor-based communications equipment employs digital signals. Converting such signals to analog for conventional multiconductor interfacing poses many inherent problems. Analog signals in multiconductor connecting interface cables have susceptibility to noise related problems, particularly in mobile environments. Such cables may also radiate or leak analog signals in various parts of the R.F. spectrum, becoming a potential source of interference with the sensitive electronic control systems of modern vehicles. Additionally, with analog signals in conventional interface approaches, the increased control and other capabilities that become available with microprocessor based equipment, would require an equally proportionate increase in the numbers of conductors interconnecting Control Units with Transceiver Units. The same applies for the required multipin connectors. It is expensive and problematic to custom hand-produce such cables and individually solder or prepare the respective multipin connectors. On the other hand, mass-producing such cables and connectors limits their versatility with respect to meeting specific and diverse customer requirements. Obviously, it would be best to employ a new approach that will employ digital techniques, allow direct interfacing of digital signals and simplify the cabling and linking of control units with the communications equipment being controlled. Ideally, such a new approach should also allow full versatility to accommodate continuous changes in network parameters and operational requirements, without requiring continuous modifications in the linking medium between the Control and Transceiver Units.
The system of this invention meets the above requirements and provides a two-way serial communications system designed for baseband digital data transmission. It utilizes a TDM-PCM (Time Division Multiplex-Pulse Code Modulation) approach. The system also allows the interfacing and linking of digitized audio. A preferred embodiment advantageously utilizes the interface system of the invention for two-way land/mobile equipment. It includes a three channel TDM-PCM serial bus operating in a synchronous, full duplex mode and utilizing the Manchester II Code. The other embodiments of the invention may use the preferred embodiment with its specific coding/formatting or other schemes with the same system of the invention.